1. Field of the Invention
The disclosures herein generally relate to a multi-feed judging device, an image forming apparatus, a multi-feed judging method, and multi-feed judging program.
2. Description of the Related Art
An image forming apparatus, a copying apparatus, and the like, with a multi-feeding detecting function detects whether recording media are transported while overlapping each other (multi-feed) or not. Such image forming apparatus detects, for example, a thickness of the recording medium and judges whether the recording media are transported while overlapping each other.
Japanese Published Patent Application No. 2009-227404 discloses detecting a position of the driven roller on transporting a recording medium and a position on not transporting the recording medium in a transporting operation by rotating a driving roller. A thickness of the recording medium is detected based on a difference between these positions of the driven roller. According to the thickness of the recording medium, it is judged whether the recording media are transported while overlapping each other.
However, the art disclosed in Japanese Published Patent Application No. 2009-227404 cannot detect precisely the thickness of the recording medium, when a motion of the position of the driven roller includes an error, in the case of continuously transporting plural recording media. Accordingly, the detecting method disclosed in Japanese Published Patent Application No. 2009-227404 has a problem that when the thickness of the recording medium cannot be detected precisely, whether the recording media are transported while overlapping each other cannot be judged.